1. Field of the Invention
The present invention relates to novel vitamin D.sub.3 derivatives, processes for the preparation thereof, and antigens comprising said derivatives for the preparation of antibodies for immunochemical assay and antibodies prepared therefrom.
More particularly, the present invention relates to novel vitamin D.sub.3 derivatives which have a carboxyl group or its ester group at the 22-position, processes for the preparation thereof, and antigens, which comprise said vitamin D.sub.3 derivative and an immunogenic carrier material for the preparation of antibodies for enzymeimmunoassay or radioimmunoassay and antibodies obtained by inoculating a host animal with said antigen for an enzymeimmunoassay or radioimmunoassay.
2. Description of the Prior Art
It has been established that vitamin D.sub.3 is metabolized in the kidney or liver into 25-hydroxy-vitamin D.sub.3, 1.alpha.,25-dihydroxyvitamin D.sub.3, 24,25-dihyroxyvitamin D.sub.3. Such metabolites as 25-hydroxyvitamin D.sub.3, 1.alpha.,25-dihydroxyvitamin D.sub.3, and such activated vitamin D.sub.3 compounds as 1.alpha.-hydroxyvitamin D.sub.3, 1.alpha.,24-dihydroxyvitamin D.sub.3, are used clinically as a remedy for osteoporosis, osteomalacia, and their development is now taking place. However, these remedies are clinically administered in very small dosages in general and a single dose is in the range of several hundreds ng to several dozens .mu.g.
On the other hand, the pharmacological action of a remedy has the interrelationship with its concentration in the serum or tissue, and the determination of the concentration of the remedy is clinically very important in the case of human beings.
As a method for the determination of the concentration of an activated vitamin D.sub.3 compound, a radioreceptor assay, wherein 1.alpha.,25-dihydroxyvitamin D.sub.3 receptor is used, has hitherto been known (Biochemistry, 13, 4091 (1974)). However, faults are found with this assay in that it demands a slow, laborious process to perform, requires large quantities of serum, and above all obtained results are not always satisfactorily accurate.
As for another assays, Japanese patent application Laid-Open No. 47653/80 discloses a radioimmunoassay wherein 1.alpha.-hydroxyvitamin D.sub.3 3-hemisuccinate or 1.alpha.,25-dihydroxyvitamin D.sub.3 3-hemisuccinate is used as a hapten. Also Japanese patent application Laid-Open No. 87344/78 discloses a radioimmunoassay wherein 1.alpha.,25-dihydroxyvitamin D.sub.3 25-hemisuccinate is used as a hapten.
In these radioimmunoassays, antigens for use in the assays are those obtained by bonding a carrier protein to a hapten by means of a carboxyl group in the substituent group at the 25-position or the 3-position of said hapten.
It is generally known that the antibody (antihapten antibody) of an antigen for assay use recognizes the chemical structure on the hapten apart from the place of its binding site to the carrier protein.
Accordingly, there is a strong probability that those antihapten antibodies obtained by use of such haptens as mentioned in the above cited patent come to have less competency to recognize the structure of the hapten at the 25-position, 1.alpha.-position, or 24-position.